Lethal build-up of ozone poses threat to UK Scientists call for global measures amid warnings that the gas damages health and the environment.

Britain is ignoring the dangers posed by one of the world's worst air pollutants: ozone.

Researchers say that levels of the gas - a powerful contributor to global warming and the cause of hundreds of deaths a year from respiratory illnesses - are rising at an alarming rate. They have also warned that measures to curtail the gas are failing. As a result, ozone-related deaths, of which there are about 1,500 a year in the UK, could rise by 50 per cent over the next decade.

Stronger international treaties need to be set up to counter the threat, they insist. 'A lot more interest needs to be taken in ozone - not only as a cause of global warming but as an immediate threat to human health and to the environment,' said Professor Piers Foster of Leeds University, an author of the most recent report from the Intergovernmental Panel on Climate Change. 'It could have a significant impact on the planet.'

Ozone is produced by the impact of sunlight on atmospheric pollutants, including car exhausts, and is strongly associated with smogs caused by traffic fumes. Hot summers, in areas polluted with nitrogen oxides and volatile organic chemicals (VOCs) emitted by vehicles, produce peak levels of ozone. Unlike ozone in the stratosphere, which protects Earth from harmful ultraviolet radiation, ozone in the lower atmosphere is harmful to humans, animals and plants.

The EU has introduced measures to reduces these pollutants, mainly by ensuring three-way converters are fitted to cars, and this has helped reduce ozone production in Europe. But countries such as Russia, China and India are still major emitters, and ozone from these nations is constantly being blown over Britain. As a result, levels are continuing to rise at a rate of 6 per cent per decade.

'The trouble is that ozone production is controlled by a patchwork of local laws and regulations,' said Professor David Fowler of the Centre for Ecology and Hydrology, Edinburgh, leader of a recent Royal Society working group on ozone. 'Weather systems and jet streams transport ozone and the pollutants that trigger its production far from its point of origin. In addition, shipping is a major producer.

'So you could introduce all sorts of measures to cut down local emissions, but these reductions would be overwhelmed by the ozone and the nitrogen oxide pollutants being swept over the country from marine and from foreign sources. Until we get an integrated network of international agreements in place, we will never get round the problem. At present no efforts are being made to set these up, however.'

Rising production of ozone is alarming because the gas is the third biggest contributor to global warming. Only carbon dioxide and methane have bigger impacts. But unlike them ozone also affects health. It is a powerful oxidant and damages lung tissue.